1. Field of the Invention
The present invention relates to pit covers for movable vehicle lift posts and, more particularly, to a displaceable shutter which retracts in the pit at both ends thereof to continuously cover the same.
2. Description of the Prior Art
In automobile and truck maintenance garages, lift posts, mostly hydraulic, are provided for elevating the vehicle in order to allow mechanics to easily work under the vehicle. Garages intended for truck maintenance require two such vertical lift posts or jacks which are positioned under the front and rear of the truck and, more particularly, under the front and rear axles thereof. As there are trucks of various lengths, the rear lift post is fixed whereas the front lift post can be displaced horizontally towards or away from the rear jack thereby accommodating different truck wheel bases. In order to allow the horizontal displacement of the mobile lift post, a slot or pit is defined in the cement floor of the garage from which protrudes at least the front jack. The width of the pit is obviously somewhat greater than the transverse dimension of the lift post and its carrying mechanism, while the length of the pit corresponds basically to the differences in wheel bases which can be encountered in various vehicles.
The open pit on the front and rear sides of the lift post represents a safety hazard to the mechanics working on the trucks at floor level. Therefore, it is common for jack retailers to include with the mobile lift post a series of removable heavy steel plates which are positioned on each side of the jack in order to close off completely the pit. When the lift post must be horizontally displaced, a proper number of these plates must be manually removed in the direction of movement of the jack to open a passage therefor, these plates being then repositioned on the other side of the lift post to close the pit. These plates being very heavy, their handling has caused many accidents, such as workmen harming their backs or falling in the pit.
Also, these plates project above the cement floor level of the garage thereby causing the mechanics to possibly trip over them and also hampering the displacements of various devices and equipments mounted on wheels or rollers.
In order to overcome some of the above problems, installations have been proposed in which the steel plates are mounted to the lift post in order to displace therewith and thus eliminate the manual handling of the plates by the workmen. U.S. Pat. 2,564,289, issued on Aug. 14, 1951 to Walker, discloses such an installation, wherein an elongated rectangular steel plate is longitudinally mounted on each of the front and rear sides of the mobile hydraulic jack so as to extend horizontally in opposite directions therefrom over the pit. Each plate has a length which is sufficient in order to close the pit for every position of the jack therealong. More particularly, the two plates are mounted to a carriage positioned around the lift post and provided with rollers engaged in horizontal channel-shaped ways recessed into the longitudinal walls of the pit. The plates slide in rectangular recesses defined in the floor on each longitudinal side of the pit and at the front and rear thereof in order that the plates are flush with the floor. The side recesses help guide the plates in a longitudinal direction, whereas the front and rear recesses are defined to accommodate the plates which project horizontally past the pit depending on the position of the jack. At each extreme horizontal position of the jack in the pit, one of the front and rear recesses will completely receive a respective plate, with the other recess defining a depression which can cause workmen to trip or can impede the handling of equipment mounted on rollers. In the intermediate positions of the jack, the front and rear recesses will each define such a depression, albeit of smaller longitudinal dimension.
U.S. Pat. No. 3,106,988 issued on Oct. 15, 1963 to Hott, is of similar structure and operating principle, although at least two longitudinally aligned horizontal plates are disposed on each side of the lift post. Also, rollers are mounted along the longitudinal sides of the pit for supporting the plates and for reducing the friction forces as they are displaced by the jack. Furthermore, Hott does not seemingly provide recesses in the floor for accommodating the plates which thus overlie the floor and protrude continuously thereabove.
In another art, it is already known to have powered shutters to close a repair pit defined in the floor of a garage with such a repair pit acting as an alternative to the above practice of elevating the vehicle with a lift for attending to the maintenance thereof. These shutters are retractable only at one end of the pit using the principle of conventional overhead garage doors. European Patent 0 115 087, issued on Aug. 8, 1984 to Schulz, discloses a typical shutter pit closure which includes a series of successive longitudinally aligned elongated panels of transverse orientation which are articulated one to the other and which are guided along horizontal rails mounted on the longitudinal upper side edges of the pit. The shutter closure is driven by a motor located in the pit which operates a pair of sprockets each engaging a chain mounted to the underside of the panels at respective transverse ends thereof. The shutter closure is further guided downwards in the pit at one end thereof when it retracts therein upon the opening of the pit.
Also known is a shutter-like closure having the mobile lift post extending therethrough and hanging freely at both its ends into the pit. Such a closure has its articulated panels supported only by the adjacent floor edges with no guidance being provided therealong, nor in the pit.
In another aspect concerning the above fixed and mobile lift posts, it is common to have the hydraulic controls for the operation thereof (horizontally or vertically) disposed on the floor. This has occasionally resulted in the inadvertent triggering of some controls while mechanics are working underneath a vehicle.
Yet another aspect of the above described pits concerns the maintenance of the lift posts. It is standard to have the underground outer cylinder of the rear fixed lift post buried in concrete or sand, whereas the front mobile lift post is in the open in the access pit. Therefore, maintenance of the front post is possible from the access thereto in the pit. On the other hand, the rear lift post is buried remote from the pit and can thus not be attended to in the event of failure without removing the sand or breaking the concrete.